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You are encouraged, but not required, to attend Shadow over Southwark in steampunky attire.

Fire Hazard

Running from a harpy.

Fire Hazard

Another adventurer finds a particularly scary, stealthy monster hiding in the bushes.

Fire Hazard

Tentaclesssssss!

Fire Hazard

Before you head out into the park, you gather at HQ, learn about the various monsters, etc.

Fire Hazard

A band of adventurers at the beginning of the game - you can tell it's the beginning because they still look so happy and gay...

Fire Hazard

It might've passed you by, but London is currently being invaded by tentacled Cthulhian horrors. I know this because, just a few nights ago, I ran screaming from them in a park in Southwark. After I'd put about 100 yards between myself and the maddening soul-sucking beasts—really, I haven't run that far or that fast since school—I caught my breath, considered the poor life choices that had led me to this pitch black woodland path, and headed back into the fray. After all, that's why I had been invited to Southwark in the first place: to close the portals being used by the monsters to slip from their dimension into ours.

Enlarge/ An incredibly rare photo of me running (away from some monster).

Fire Hazard

That is the rough premise of Shadow over Southwark, the latest immersive game from Fire Hazard Games. Basically, you walk (and occasionally run) around the park looking for the answers to clues. Harder, more cryptic clues net you more points. There are multiple teams running around the park, consisting of between two and six people, and ostensibly you are competing with each other—but in reality, once you bump into a few of the creatures that roam the park, you begin to feel the bonds of camaraderie.

There are three types of monster in Shadow over Southwark: harpies, shogghasts, and waldgeists, all played by actors in really quite convincing costumes. If you get too close to one of these extradimensional spawns of evil, they suck out your soul (you lose points). Each monster has fairly simple mechanics—the harpy patrols a set route and runs in straight lines; the shogghast can't see you if you stand still; and the waldgeist is camouflaged, hoping that you stumble into it—but when you're already using your brain to navigate and solve clues, the monsters add just enough stress to make the whole experience rather fun (or scary, depending on your disposition).

There are a few more details—Fire Hazard has put a lot of effort into making this game more than just a glorified scavenger hunt—but I don't want to spoil it. Shadow over Southwark is fun, fantastically performed (there are other actors who are on your side), and well worth 25 of your hard-earnt pounds. But... it's the clever technology that underpins the entire game that really caught my eye.

The contents of the pouch worn by each of the monsters.

Fire Hazard

Fire Hazard

Immersive game tech

When you arrive at HQ for your briefing, you are handed an amulet and told to put it on; you're told it'll ward away the shadows, or something to that effect. Actually the amulet contains a Bluetooth 4.0 LE beacon that constantly transmits your player ID number. The game also requires each person to open a special website on their smartphone; the website is how you see the clues, and also where you enter the answers once you work them out.

Enlarge/ At the start of the game you receive a codex, which contains awesome sketches like this. (This is a waldgeist.)

Fire Hazard

Then, on the other end, each monster is equipped with a black pouch that contains a £50 Moto E phone, an IOIO microcontroller dev board, a 15 watt amplifier, a speaker, a big ol' red LED bulb, and a 12V lithium-polymer battery pack that powers the whole thing. Built by Fire Hazard's founder, a nerdy software guy called Gwyn, the equipment has a distinct DIYish feel.

When triggered by a switch in the actor's hand, the red light turns on, an unearthly wail plays through the speaker, and the phone—which is running an Android app that was written specifically for this game—starts looking for Bluetooth beacons. Any beacons that are within a certain range (i.e. beacons above a defined signal strength) are packaged up and transmitted via the phone's 4G connection to a remote Web server.

The server decides which teams should be penalised—you only get penalised once per team, even if all your beacons are in range of the monster—and uses websockets to send a notification to the players on those teams. If you have the website open on your phone, there's a JavaScript application that receives the notification and plays a sound effect to let you know that your soul is being stolen. The whole process—from the actor activating the switch, to you losing your soul—takes about one second.

Bugs, bugs, bugs

As you'd expect from a game system with DIY hardware and made-from-scratch software, Shadow over Southwark isn't without its bugs. The Bluetooth amulets can run out of battery, for example. And Bluetooth itself is omnidirectional; you might not be able to see the monster, but your soul can still be sucked out through a big hedge if you're unlucky.

One issue that afflicted me was an open BT Wi-Fi hotspot. My phone automatically hopped onto the Wi-Fi, disconnecting me from 4G and thus preventing me from entering a time-sensitive answer. This can be easily fixed by turning Wi-Fi off, or turning off auto-join, before you start playing.

I also noticed that, whenever an actor flipped the switch, there was the unmistakable whine of interference. Later, when I was being shown the technology, Gwyn confirmed that it really was interference: the audio cable to the speaker isn't shielded or grounded, so they were picking up interference from the phone, which was then being amplified. Gwyn said that the next build of the system will fix the problem (which they've affectionately dubbed "radio waldgeist").

The next build will also replace the IOIO dev boards with custom-etched PCBs that'll be more general-purpose and can be more easily adapted to other Fire Hazard games; right now, the hardware for each Fire Hazard game is completely bespoke. (The Web-based server that hosts the game, though, is used by other Fire Hazard games such as Citydash.)

Immersive games are super cool

Shadow over Southwark was my first immersive game, and it was seriously cool. I was sceptical about spending my Saturday night running around a park, but that scepticism quickly vanished when I got out of my car and a portly professor type in Victorian-cum-steampunk clothing started hurrying me towards headquarters, loudly intoning that "The other adventurers are waiting!"

Further Reading

The game was well produced, the gothic-Cthulhian horror well executed, and the clues were reasonably taxing. If you're a tech nerd like me, the game's tech underpinnings really took it to the next level—but judging by the screams that tore through the darkness that night, and the increasingly frenetic mood as we were mobbed by abyssal terrors, I don't think many players were thinking about the technology. Which is exactly how technology should be.

Shadow over Southwark runs until the end of November, on Thursday, Friday, and Saturday night. The run may be extended until Christmas, however, due to high demand. Fire Hazard runs other immersive games in London (Citydash and Raiders of the Lost Archive), and indeed in a few cities around the world (currently Durham and Adelaide in Australia.)

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Sebastian Anthony
Sebastian is the editor of Ars Technica UK. He usually writes about low-level hardware, software, and transport, but it is emerging science and the future of technology that really get him excited. Emailsebastian@arstechnica.co.uk//Twitter@mrseb